Girard Perregaux Constant Escapement

Girard-Perregaux Constant Escapement: A real revolution

The history of watchmaking, like that of car-manufacturing or computer software, is a long succession of novel and revolutionary inventions, some of which remain little known due to the marketing or manufacturing difficulties they presented.

By Malik Bahri

The numerous explorations on escapement are a telling example of these “subconsciously deliberate” mistakes. By perfecting constant escapement today, Girard-Perregaux furthers a research that began over two centuries ago on natural escapement.

A few months ago, George Daniels’ Space-Dweller was propelled to the astronomical worth of 1.6 million CHF by a thump of Geoffrey Ader’s gavel at Sotheby’s. This pocket watch, which indicates both sidereal and solar time, also possesses a peculiar feature: a double escapement, a George Daniels specialty, directly inspired by the works of Abraham Louis Breguet, specifically those pertaining to ‘natural’ escapement. The latter is the least known of the three escapements developed around that period:

- The lever escapement, featured in 99% of contemporary watches. It presents the dual advantage of relative precision, since each beat provides an impulse to the balance wheel, allied to sturdiness. It does have one drawback, however. Being an indirect form of escapement, it requires important lubrication. 

- The rare detent escapement, mainly found on marine chronometers and some vintage precision pocket watches. It is difficult to adjust and is very sensitive to shocks, as the impulses are only given to the balance with every other swing. This type of escapement might gain popularity with the rise of high frequency and anti-shock watches, as these could allow for its sensitivity while helping it withstand brutal movements.

- Finally, the double wheel escapement. Although it combines the virtues of detent escapement and lever escapement (direct escapement + transmission of each impulse), it also combines their drwabacks, meaning it is somewhat fragile and prone to premature wear because of the high friction resulting from its mechanical complexity.

Today Girard-Perregaux draws inspiration from past research on the natural escapement to create a groundbreaking type of escapement: the constant escapement.

Before we delve into the workings of this escapement, a reminder on the principle of constant force: a spring barrel, as any energy accumulator, holds tension. This tension is high at the start of the power reserve, medium halfway through and low at the end. To minimize degradation of chronometrical performances, braking systems exist that refrain the spring of the barrel before it loses all energy. Less frequently, other techniques are applied to regulate the barrel’s energy:  a mini spring, with a short reload, may be implanted before the power chain to regulate the energy from the barrel.

But the solution proposed by Girard-Perregaux is innovative, as it does not intervene before the regulating organ, but after. Better still, it operates directly upon the escapement, the most delicate piece in a mechanical watch. 

A natural escapement consists of a pair of double escapement wheels and a roller with impulse pallets, directly affixed to the axis of the balance wheel. The roller is equipped with a stopping device. The impulse pallets set the epicycloidal wheels into motion, and they in turn set the coaxial wheels with pointed teeth forward, while their progress is braked by the arbor linked to the roller.

Was that clear? Excellent ! Now get this: although Girard-Perregaux’s offering keeps the double wheel escapement and direct impulse, it modifies and revolutionizes everyhing else. The greatest novelty the MVT-009100-0007 caliber brings about is an unprecedented intermediate part made up of a silicon buckled blade upon a frame.

The blade is attached to this particular anchor frame, which takes its origin at the axis of the balance wheel and runs along to the two escapement wheels. The latter do not interact but, rather, rest on the anchor frame.

The uniqueness of this anchor frame resides in the fact that it is regulated by the silicon blade attached to the plate. This silicon ‘thread’ oscillates at constant speed according to the principle of buckling: the oscillation of a flexible body, from its compression point to its flexion point.  An experiment easily reproduced with, say, a business card.

The bulk of the work resided in shaping a silicon blade unstable enough (but still with a degree of constancy) in order to allow oscillation to occur upon the least little impulse of the balance wheel. That way, whether fed feeble or considerable energy, the blade regulates the signal transmitted by the balance wheel. The blade itself is only 14 microns, about a sixth of one human hair, and its creation required the help of the Swiss Center for Electronics and Microtechnology (CSEM), while the DRIE (deep reactive ion Etching) technique, previously used for silicon balance-springs, was called upon to finalize its shape.

CSEM technology behind Girard-Perregaux Constant Escapement video

CSEM is a private applied research and development center specializing in micro- and nanotechnology, system engineering microelectronics and communications technologies based in Neuchâtel. 

It mission is to enhance the competitiveness of industry, particularly Swiss industry, by developing applied technology platforms in micro- and nanotechnologies and ICT and transferring them to the industrial sector.

This escapement operates, then, through over-regulation of the balance wheel’s energy. Beyond the purely technical aspects, its workings are beautiful to behold, as this video demonstrates.

For this mechanism to make sense, it had to propose a great power reserve: 7 days. Two spring barrels of 150 cm each power the barrel at a rate of 21600 v/h. The movement is of 17’’’ ½ (for a width of 8’’’) and consists of 271 elements and 28 rubies. Given the size of the movement, the white gold case is relatively big at a diameter of 48mm for a width of 14,63mm.  

But the aesthetical impact, of course, rests not in the case. It rests in the exceptionally cut out movement. The way in which the iconic three bridges from Girard-Perregaux are integrated to the escapement, although subtle, cannot fail to catch the eye. The linear power reserve is located at 9 o’clock on the dial, while the hour and minute stand at noon. The back of the case boasts a very superior finish: with expressive skeletonized bridges and perfectly thought out contrasts between the different galvanized colors, it is gorgeous, original and the symmetry struck between the right and left halves is such as has rarely been achieved. 

The Constant Escapement is the first watch to integrate an escapement that ventures so far from the principles of natural escapement to take state of the art technology in its stride. To make such an ensemble work, by going forward with revolutionary principles.

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